Method and apparatus for transporting data using label switching

ABSTRACT

A method including receiving a call connection request message having a prefix number and determining a corresponding IP address based on the prefix number. Then, assigning a label based on the corresponding IP address. Further, routing the call connection request message based on the label. An apparatus implementing the method described above.

FIELD OF THE INVENTION

This invention relates to network infrastructures. Specifically, thisinvention is directed towards a method and apparatus for transportingdata using label switching.

BACKGROUND

Proposals are frequently submitted to standardization bodies, orgenerally discussed among technology experts, that describe how tointegrate, transport and consolidate traditional central office (CO)based voice services (e.g., plain old telephone services (POTS)) overnext generation infrastructures such as Asynchronous Transfer Mode (ATM)infrastructure.

In the interim, standards bodies such as the InternationalTelecommunications Union (ITU) have defined a series of standards thatare often regarded as the way to achieve this integration. Thisinfrastructure is known as the ATM-Broadband Integrated Services DigitalNetwork (B-ISDN) infrastructure. However, this infrastructure could facescaling and voice quality issues as it simply represents an overlaysolution with its inherent issues. For example, the currentinfrastructure is based on a circuit-based network, which is limited inits numbering and addressing capabilities.

In addition, this new infrastructure will ultimately be based onInternet Protocol (IP), or an evolutionary form of IP. Specifically, theservice layer will be fully IP-based and the transport layer will eitherbe IP or ATM. Thus, it would be desirable to have a technology toprovide large-scale integration of voice traffic that works on bothtechnologies seamlessly, and yet is able to deliver theconnection-oriented nature and the quality of service guarantee thattraditional voice service requires.

SUMMARY

It is therefore an object of the present invention to simplify signalingflows across the network.

It is a further object of the present invention to reduce the signalingburden on call processors within the core network.

It is yet a further object of the present invention to optimally takeadvantage of the new, emerging infrastructure, and elegantly combine IP,ATM and voice technologies—keeping their protocol stacks separate andintact, and eliminating the need for very extensive mapping of signalingaspects between the different technologies.

These and other objects of the invention are provided by a system thatprovides connectivity establishment based on the topology of the voicenetwork, but not requiring the individual user initiated call requeststo be individually established within the core network. The individualcall requests are tunneled through the core network, and the callrequests are only established within and among the edge voice centraloffices. In one embodiment, the process involves receiving a callconnection request message having a prefix number. Then, determining acorresponding IP address based on the prefix number, and assigning alabel based on the corresponding IP address. Further, routing the callconnection request message based on the label.

Other objects, features, and advantages of the present invention will beapparent from the accompanying drawings and from the detaileddescription that follows below.

BRIEF DESCRIPTION OF THE DRAWINGS

The system is illustrated by way of example and not limitation in thefigures of the accompanying drawings in which like references indicatesimilar elements and in which:

FIG. 1 is a block diagram of connectivity establishment over a prior artintegrated services digital network.

FIG. 2 is a block diagram of issues present with connectivityestablishment in the prior art network of FIG. 1.

FIG. 3 is a block diagram of a network infrastructure configured inaccordance with one embodiment of the present invention.

FIG. 4 is a diagram illustrating an MPLS connection establishment for avoice infrastructure configured in accordance to one embodiment of thepresent invention.

FIG. 5 is a flow diagram for an MPLS connection establishment procedureaccording to one embodiment of the present invention.

DETAILED DESCRIPTION

In order to support large scale voice architectures, a transportsolution for large scale voice services based on tag switching and IP isproposed. In one embodiment, voice switches located in central offices(CO) implement the service at the edge node layer (e.g., the nodes thatare at the edge of the network), surrounding the IP/ATM infrastructure.An IP “adjunct processor” (e.g., a router) extends the capability of theCO to allow the CO to (1) maintain an IP address and (2) communicateusing a robust IP routing protocol. These CO's with the extended IPcapability set are referred to as next generation central offices(ngCO's). All ngCO's in the network implement the multi-protocol labelswitching (MPLS) (also known as tag switching) protocol stack. MPLS isdescribed in the Internet Engineering Task Force (IETF) Request ForComments (RFC) 2105, titled “Cisco Systems' Tag Switching ArchitectureOverview”, authored by Y. Rekhter, B. Davie, D. Katz, E. Rosen, and G.Swallow, a copy of which is located at http://www.ietf.org.

ngCOs connect to the IP-ATM infrastructure, which is alsotag-switching/MPLS-based, by using the tag switching/MPLS labeldistribution protocol and IP routing protocol (or, when available, nextgeneration IP routing protocol). ngCO's exchange topology informationand request connectivity (labels) to connect to other ngCO's. Theconnectivity is established using labels that identify permanent virtualpaths (PVP's) with guaranteed quality of service (QoS) parameters. ThengCO's dynamically map voice connections onto these pre-establishedPVP's, and thus user calls are tunneled through the infrastructure. Manyadditional features that increase reliability such as overflow routingor intelligent network services may be defined using this model.

FIG. 1 is a block diagram of connectivity establishment over a prior artintegrated services digital network 100. Network 100 includes a firstvoice CO 102, a first ATM CO 104, a second ATM CO 106, and a secondvoice CO 108.

First voice CO 102 and second CO 108 are edge CO's responsible fortransferring received ISDN calls to ATM CO's such as first ATM CO 104.The voice CO's maps a user's call into a Signal System 7 (SS7) initialaddress message (IAM) to attempt to establish a connection. A staticrouting table contained on the CO is used to determine the destinationfor the connection establishment attempt. CO's are connected throughtrunk lines, where multiple trunk lines may be used between each CO.

ATM CO 104 and ATM CO 106 are part of a broadband network 110. The ATMCO's performs ISDN User Part (ISUP) to broadband ISUP (B-ISUP)internetworking. The ISUP signaling protocol, as defined by the AmericanNational Standards Institute (ANSI), is an out-of-band signalingtechnique used for call set up and tear down over the SS7 network. ISUPtransfers call set-up information between signaling points (SP) in anSS7 network. The ATM CO's uses ISUP to set up a virtual channel for eachvoice call.

In FIG. 1, a user A, which is coupled to voice CO 102, is trying toestablish a voice call with a user B coupled to voice CO 108. User Asends a call request to voice CO 102, which maps the request to a SS7IAM in order to attempt to establish a connection. As noted above, astatic routing table is used to determine the destination for theattempted connection establishment. In the example illustrated by FIG.1, where user B's phone number is 408-555-7081, voice CO 102 looks upthe trunk line that should be used for routing the call request in alocal routing table by using “408-555.” In this example, the area code(e.g., “408”) and the prefix (e.g., “555”) is used to determine thattrunk 1 is to be used to forward the call request. Thus, the callrequest is forwarded to ATM CO 104. ATM CO 104, based on its localrouting table, forwards the call request on trunk 2 to ATM CO 106, andATM CO 106 forwards the call request to voice CO 108 based on the sameprotocol. Voice CO 108 then determines that the call request should beforwarded to user B.

FIG. 2 is a block diagram of issues present with connectivityestablishment in network 100 of FIG. 1. Network 100 contains a set ofvoice CO's 202 a–202 d similar to voice CO 102 and voice CO 108. Eachone of set of voice CO's 202 a–202 d services a set of users 204 a–204d, respectively. Set of voice CO's 202 a–202 d are also connected tobroadband network 110, containing a set of ATM CO's 206 a–206 b. Asshown in FIG. 2, each user requires a single link through network 100,and each link is individually mapped from point-to-point (e.g., eachlink is individually mapped from one user to another user).

The individual mapping creates several issues, including concentrationof connection setup requests in the broadband infrastructure (e.g.,broadband network 110), administrative lack of transparency, requiredvisibility of very small 64 kbit/s channels when compared to themulti-gigabit/s broadband network channels, and lack of transparency inrouting topology. Moreover, one to one mapping requires that each 64kbit/s channel to be individually handled to the segmentation andreassembly layer during processing, which increases the end-to-end delaypenalty, and making echo compensation an issue.

FIG. 3 illustrates network 100 including a set of IP-adjunct processors(IP-AP) 306 a–306 b connected to a set of voice CO's 304 a–304 b. EachIP-AP in set of IP-AP's 306 a–306 b has an associated IP address andcommunicates with devices in an IP+ATM network 302 using the IP routingprotocol.

Set of IP-AP's 306 a–306 b tunnel the initial address messages usingpre-established labels such that 64 kbits/s connections may be tunneledthrough IP+ATM network 302. The 64 kbits/s connections would beconverted into packetized data and may be packed along with otherpacketized data from other 64 kbit/s connections into ATM cells fortransfer. Once the 64 kbits/s connections have been packed into cells,the IP+ATM CO's in IP+ATM network 302 simply has to handle them usingstandard MPLS. Connections would be established using voice networktopology messages.

For example, in FIG. 3, user A is attempting to establish a connectionwith user B, who has a phone number of 408-555-7081. A call request issent to voice CO 306 a, which uses its internal static routing table todetermine that call requests to the prefix of “408-555” should be sentover trunk 1. Trunk 1 reaches IP-AP 304 a, which from the prefix of“408-555” determines through a dynamic routing table that this callrequest would be handled by a device with an IP address of 128.56.43.87.Using the routing table, IP-AP 304 also determines that the call requestshould be sent over logical link labeled link 9, which is to IP+ATM CO308 a.

Once IP+ATM CO 308 a receives the data, it determines that the callrequest should be sent over link 2. The determination is made using alocal label routing table containing a list of MPLS labels with theircorresponding destination links. Thus, once the call request isconverted into the label switched network, the call request may betreated as other data in IP+ATM network 302, such that the data ispackaged into cells and allows for routing based on the standards usedin IP+ATM network 302. IP+ATM CO 308 b then receives the call requestand forwards the request to IP-AP 304 b, which forwards the request tovoice CO 306 b. Voice CO 306 b then uses a local static routing table todetermine the call request should go to line B, associated with user B.

Before IP-AP 304 b may be reached, it must broadcast its IP address,along with the associated prefixes that its associated voice CO (e.g.,voice CO 306 b) supports, before the system can begin to route calls toIP-AP 304 b and voice CO 306 b. In one embodiment, the numbers of whichthe prefix is a part of are based on the ITU standards on numbering andaddressing (ITU standard E.164). The E.164 standard specifies a phonenumber in a country code and a national significance number (CC+NSN)format. The NSN format is left to the national body to further defineand thus may be different for country to country. In one embodiment, afixed portion of the NSN is chosen to be the prefix number.

FIG. 4 and FIG. 5 illustrate the set-up process for voice CO 306 a andIP-AP 304 a. In FIG. 4, is a simplified diagram of FIG. 3, and voice CO306 a is represented by a voice CO 402. Similarly, IP-AP 304 a isabstracted by an IP-AP 404. The first step in the process, in block 502,is for voice CO 402 to pass a prefix table to IP-AP 404. The prefixtable lists the prefixes voice CO 402 supports (e.g. “408-555”) and theassociated phone lines attached to voice CO 402 (e.g., “A”–“n”). VoiceCO 402 may support many hundreds of thousands of users (e.g., phonelines) and thus support multiple prefixes. For example, voice CO 402 mayalso support prefix “408-556”).

After voice CO 402 has transferred its prefix table to IP-AP 404 inblock 502, IP-AP 404 updates its local prefix-IP routing table (whichwas also referred to as the dynamic routing table in the descriptionaccompanying FIG. 3) in block 504. Then, in block 506, IP-AP 404 “links”all prefixes in the prefix table received from voice CO 404 to an IPaddress of IP-AP 402 by broadcasting the IP address and the prefixesfrom the prefix table in an update message. For example, the updatemessage is sent to IP-AP 406, which services voice CO 410, and also sentto IP-AP 408, which services voice CO 412. Thus, all other IP-AP's inthe network are updated via topology update messages, which allow eachIP-AP to update local routing tables to include the topology updateinformation in block 508, thus establishing connectivity to prefix anduse.

The IP-AP for voice CO switches extends the capabilities of existingvoice CO switches and allows these voice CO switches to communicateusing IP routing protocols. These adjunct processors implement broadbandIP or ATM interfaces to the core network. As core infrastructureswitches only have to implement tag switching/MPLS, no majorarchitectural changes are required. It is crucial, though, that qualityof service guarantees required by the voice service (predictable lowdelay) are very strictly supported, and fully isolated from otherservice categories in the network. It is noted that the functionalityprovided by each IP-AP may be integrated into each voice CO switch, andthereby reducing the need to service a separate component from voice COswitch.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

1. A method comprising: receiving a telephony call connection requestmessage having a prefix number; determining a corresponding IP addressbased on the prefix number; assigning a label based on the correspondingIP address; sending data from other established connections to anetwork, the data from the other established connections also taggedwith the label; and, tunneling a request that is derived from thetelephony call request message through the network by routing therequest with other established connections through the network based onthe label.
 2. The method of claim 1 further including: creating an entryin a routing table containing an IP address and a set of prefix numbersassociated to the IP address, the IP address being assigned to a centraloffice that handles calls for the set of prefix numbers.
 3. The methodof claim 2, further including: transmitting an update message containingthe IP address and the set of prefix numbers.
 4. The method of claim 1,where the prefix number is in a format conforming to ITU E.164,representing a set of numbers having a country code portion and anational significance portion.
 5. An article comprising a computerreadable medium having instructions stored thereon, which when executed,causes: receiving a telephony call connection request message having aprefix number; determining a corresponding IP address based on theprefix number; assigning a label based on the corresponding IP address;sending data from other established connections to a network, the datafrom the other established connections also tagged with the label; and,sending a request with the label to the network so that the request canbe tunneled through the network with the other established connectionsthat are transported through the network with the label, the requestderived from the telephony call connection request message.
 6. Thearticle of claim 5, wherein the computer readable medium further havinginstructions stored thereon, which when executed, causes: creating anentry in a routing table containing an IP address and a set of prefixnumbers associated to the IP address, the IP address being assigned to acentral office that handles calls for the set of prefix numbers.
 7. Thearticle of claim 6, wherein the computer readable medium further havinginstructions stored thereon, which when executed, causes: transmittingan update message containing the IP address and the set of prefixnumbers.
 8. The article of claim 5, where the prefix number is in aformat conforming to ITU E.164, representing a set of numbers having acountry code portion and a national significance portion.
 9. Anapparatus for transporting data using label switching comprising: aprocessor; a computer readable medium having instructions storedthereon, which when executed, cause the processor to: receiving atelephony call connection request message having a prefix number;determining a corresponding IP address based on the prefix number;assigning a label based on the corresponding IP address; sending datafrom other established connections to a network, the data from the otherestablished connections also tagged with the label; and, sending arequest with the label to the network so that the request can betunneled through the network with the other established connections thatare transported through the network with the label, the request derivedform the telephony call connection request message.
 10. The apparatus ofclaim 9, where the computer readable medium further having instructionsstored thereon, which when executed, causes the processor to: create anentry in a routing table containing an IP address and a set of prefixnumbers associated to the IP address, the IP address being assigned to acentral office that handles calls for the set of prefix numbers.
 11. Theapparatus of claim 10, where the computer readable medium further havinginstructions stored thereon, which when executed, causes the processorto: transmit an update message containing the IP address and the set ofprefix numbers.
 12. The apparatus of claim 9, where the prefix number isin a format conforming to ITU E.164, representing a set of numbershaving a country code portion and a national significance portion. 13.An apparatus, comprising: means for receiving a telephony callconnection request message having a prefix number; means for determininga corresponding IP address based upon the prefix number; means forassigning a label based on the corresponding IP address; and, means fortunneling a request derived from the telephony call connection requestmessage through a network by routing the request with other establishedconnections through the network based on the label.
 14. The apparatus ofclaim 13 further comprising means for creating an entry in a routingtable containing an IP address and a set of prefix numbers associated tothe IP address, the IP address being assigned to a central office thathandles calls for the set of prefix numbers.
 15. The apparatus of claim14 further comprising means for transmitting an update messagecontaining the IP address and the set of prefix numbers.
 16. Theapparatus of claim 13 further comprising means for representing a set ofnumbers having a country code portion and a national significanceportion when the prefix number is in a format conforming to ITU E.164.17. A method, comprising: receiving a telephony call connection requestmessage having a prefix number; determining a corresponding IP addressbased upon the prefix number; assigning an MPLS label based on thecorresponding IP address; and, sending a message having the MPLS labelto a network so that a request for the telephony call can be tunneledthrough the network by being transported along with data from otherestablished connections based upon the MPLS label.
 18. The method ofclaim 17 where the network further comprises an IP service layer and anATM transport layer.
 19. The method of claim 18 where the callconnection request message is an SS7 IAM message.
 20. The method ofclaim 18 where the prefix number is an ITU E.164 compatible prefix. 21.The method of claim 17 where the call connection request message is anSS7 IAM message.
 22. The method of claim 17 where the prefix number isan ITU E.164 compatible prefix.
 23. An apparatus, comprising: means forreceiving a telephony call connection request message having a prefixnumber; means for determining a corresponding IP address based upon theprefix number; means for assigning an MPLS label based on thecorresponding IP address; and, means for sending a telephony messagehaving the MPLS label to a network so that a request for the telephonycall can be tunneled through the network by being transported along withdata from other established connections based upon said the MPLS label.24. The method of claim 23 where the network further comprises an IPservice layer and an ATM transport layer.
 25. The method of claim 24where the call connection request message is an SS7 IAM message.
 26. Themethod of claim 24 where the prefix number is an ITU E.164 compatibleprefix.
 27. The method of claim 23 where the call connection requestmessage is an SS7 IAM message.
 28. The method of claim 23 where theprefix number is an ITU E.164 compatible prefix.